Conductivity is a parameter used to describe the ease with which electric charge flows in a substance. In the formula, conductivity is represented by the Greek letter σ. The standard unit of conductivity σ is Siemens/meter (abbreviated as S/m), which is the reciprocal of resistivity ρ, that is, σ=1/ρ.
When 1 ampere (1 A) current passes through the cross-section of an object and there is a voltage of 1 volt (1 V), the conductivity of the object is 1 S. Siemens is actually equivalent to 1 ampere/volt. If G is the conductivity (unit Siemens), I is the current (unit ampere), and U is the voltage (unit volt), then: G = I/U
The conductivity σ can be calculated by the conductivity G, the cross-sectional area of the conductor A, and the length of the conductor l: σ = Gl/A